Hydraulic valve lifter

ABSTRACT

A self-adjusting hydraulic valve lifter for an overhead cam engine wherein this pressure fed hydraulic valve lifter is interposed directly between a valve and cam, the lifter including an upright, cup-shaped plunger engaging on the valve stem and being reciprocally received in a larger, inverted, cup-shaped follower which engages the cam and which is slidably guided in a fixed bore surrounding the valve stem, a pressure chamber being formed between an end of the plunger and the follower, with a helical compression spring positioned therein to normally bias the plunger and follower against the valve stem and the cam, respectively, and a fluid supply passage is provided to supply fluid under pressure to the pressure chamber, the fluid supply passage including a V-shaped groove with an O-ring seated therein to serve as a one-way check valve controlling the flow of fluid to the pressure chamber.

United States Patent [1 1 Morgan HYDRAULIC VALVE LIFTER [75] Inventor:Robert E. Morgan, Grand Rapids,

Mich.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

221 Filed: Aug. 21, 1974 21 Appl. No.: 499,272

[52] US. Cl 123/9055; 123/9016 [51] Int. Cl. ..F0111/14 [58] Field ofSearch 123/9055, 90.56, 90.16

[56] References Cited UNITED STATES PATENTS 2,175,467 10/1939 Johnson123 9055 2,580,380 l/l952 Banker 123/9055 2,580,382 1/1952 Banker123/9055 3,286,702 11/1966 Dadd 123/9055 3,509,858 5/1970 Scheibe123/9055 3,658,038 4/1972 Bergmannm. 123/9055 3,704,696 12/1972 Abell123/9055 1 Apr. 15, 1975 Primary ExaminerManuel A. Antonakas AssistantExaminerDaniel J. O'Connor Attorney, Agent, or Firm-Arthur N. Krein [57] ABSTRACT A self-adjusting hydraulic valve lifter for an overhead camengine wherein this pressure fed hydraulic valve lifter is interposeddirectly between a valve and cam, the lifter including an upright,cup-shaped plunger engaging on the valve stem and being reciprocallyreceived in a larger, inverted, cup-shaped follower which engages thecam and which is slidably guided in a fixed bore surrounding the valvestem, a pressure chamber being formed between an end of the plunger andthe follower, with a helical compression spring positioned therein tonormally bias the plunger and follower against the valve stem and thecam, respectively, and a fluid supply passage is provided to supplyfluid under pressure to the pressure chamber, the fluid supply passageincluding a V-shaped groove with an O-ring seated therein to serve as aone-way check valve controlling the flow of fluid to the pressurechamber.

7 Claims, 4 Drawing Figures HYDRAULIC VALVE LIFTER This inventionrelates to hydraulic valve lifters or tappets, such as are used, forexample, in maintaining substantially zero lash in valve operatingmechanism of an internal combustion engine and, in particular, to aselfadjusting hydraulic valve lifter for use in an overhead cam engine.

Various forms of hydraulic valve lifters or tappets of the type for usespecifically in overhead cam engines are known and these generallyinclude a lifter body or follower within which a plunger or piston isslidably po sitioned either directly in the follower, per se, or in acylindrical, inner cup member which, itself, is slidably positioneddirectly in the follower. In most of the known hydraulic valve lifters,the plunger thereof is provided with a central passage and an inlet ballcheck valve is used to control flow through this central passage to avariable volume hydraulic pressure chamber defined, in part, by one endof the plunger, the hydraulic lifter further including a springpositioned to abut against the plunger to normally move it in adirection to increase the volume of the hydraulic pressure chamber.

It is therefore a primary object of this invention to provide animproved hydraulic valve lifter structure whereby a single, annular,ring valve is used as a oneway check valve for controlling fluid flow toa pressure chamber within the valve lifter.

Another object of this invention is to improve a hydraulic valve lifterwhereby it can be easily fabricated with a minimum of parts. the lifterincorporating as an element thereofan O-ring of resilient material whichin a preferred embodiment functions both as a one-way check valve and asa retainer for a plunger within a follower element of the lifter.

These and other objects of the invention are obtained by a hydraulicvalve lifter which includes an inverted, cup-shaped follower having astepped bore therein to slidably receive a spring biased, cup-shapedplunger forming with the follower a pressure chamber supplied with oilthrough a feed hole in the follower and a V- shaped groove incommunication with the feed hole, the V-shaped groove opening into thepressure chamber with flow therefrom controlling by an O-ring valvenormally seated in the V-shaped groove.

For a better understanding of the invention, as well as other objectsand further features thereof, reference is had to the following detaileddescription of the invention to be read in connection with theaccompanying drawings. wherein:

FIG. 1 is a transverse, sectional view through the upper portion of aninternal combustion engine incorporating a hydraulic valve lifter inaccordance with the invention;

FIG. 2 is an enlarged, fragmentary, sectional view taken substantiallyalong the lines 22 of FIG. 1 showing a preferred embodiment of ahydraulic valve lifter in accordance with the invention;

FIG. 3 is a view corresponding to FIG. 2 showing an alternate embodimentof the hydraulic valve lifter; and,

FIG. 4 is a view corresponding to FIG. 3 illustrating still anotheralternate embodiment of the hydraulic valve lifter.

Referring now in detail to the drawings and, in partie ular, to FIG. 1,an engine cylinder block I is shown as having a cylinder 2 in which anengine piston 3 operates in the usual manner. Covering the upper end ofthe cylinder 2 is a cylinder head 4 in which a poppet valve 5 isslidably fitted to control and closing of the port 6 communicating withthe combustion chamber 7 above the piston. The valve 5 is biased to itsnormally closed position shown by a coil spring 8. Downward actuation ofthe valve 5 in the opening direction is effected by a cam 9 on acamshaft I0 which directly overlies the upper end of the valve stem IIand which is suitably journalled in a housing I2 bolted to the cylinderhead.

A hydraulic valve lifter or tappet, generally designated 14, andhereafter referred to as the valve lifter, is reciprocally journalled ina lifter guide bore 15 in the housing 12 and is interposed directlybetween the cam 9 and the valve stem 11. Hydraulic fluid in the form ofoil from the engine lubricating system, now shown, is supplied undermoderate pressure via an oil gallery 16 and a branch port 17 to thevalve lifter 14, the branch port I7 extending to the lifter guide bore15.

Referring now to FIG. 2, there is illustrated a preferred embodiment ofa valve lifter 14, in accordance with the invention, which includes aninverted, cupshaped, cylindrical outer member or follower 20 having aclosed, upper head or end wall 21 which is in abutting engagement withcam 9, a depending outer skirt 22, de' fining a substantiallycylindrical recess, and a central boss 23, the skirt 22 and a centralboss 23 being inter connected by spaced apart webs 24 integral therewithand with the end wall 21. The central boss 23 is pro vided with acylindrical stepped bore which includes a bore 25 extending from thefree end of the boss and an enlarged bore 26 at the opposite end whichterminates at the interior surface of the end wall 21, the bores 25 and26 meeting coaxially with an intervening shoulder 27.

The valve lifter 14 further includes a cylindrical plunger 30 of anupright, cup-shape configuration which is slidably received in the bore25 and extending into bore 26 within the follower 20, the plunger 30having a closed, lower head or end wall 31 for abutting engagement withthe valve stem 11. Plunger 30 is provided with a stepped bore 32 at itsupper end to receive one end of a helical wound compression spring 40which at one end abuts against a suitable abutment, in the form of ashoulder 33 in the plunger, while the opposite end of spring 40 abutsagainst the interior surface of the end wall 21 of follower 20 wherebythe follower 20 and plunger 30 are normally biased into contact with thecam 9 and valve stem I 1, respectively.

The follower 20 and plunger 30 cooperate to form a fluid chamber 41within the follower 20, above and around the upper end of the plunger30, and specifically around that portion of the plunger 30 which extendsout into the enlarged bore 26 within the follower 20. This fluid chamber41 is supplied with engine oil under presure from the oil gallery 16 andbranch port 17 via an outer annulus or annular groove 42 provided forthis purpose around the outer peripheral surface of the follower 20, thegroove 42 being in communication via one or more radial extending portsor passages 43, only one being used in the embodiment shown, in the web24 and boss 23 of the follower 20 with an inner annulus or annulargroove 44 in the boss 23 formed con centric with the bore 25 therein.

Oil supplied to the groove 44 flows via a radial passage or side port 34in plunger 30 to an axial passage 35 extending from the upper or openend of the plunger, this end then being suitably closed as by a ballplug 36 suitably fixed in the end of this passage in the upper end ofthe plunger 30. The axial extending pas sage 35 is in fluidcommunication with the apex or bottom of a substantially V-shaped groove37 formed on the outer periphery of the plunger 30 closely adjacent toits open or upper end. that is, the portion of the plunger normallyextending into the enlarged bore 26 in follower 20, with the V'shapedgroove 37 formed to open outward into fluid chamber 41. Flow from thepassage 35 through the Vshaped groove 37 is con trolled by a one-waycheck valve in the form of an annular ring or O-ring 45, as it isnormally referred to, which is made of a suitable resilient material,such as synthetic rubber. The O-ring valve 45 is of a size to seatwithin the V shaped groove in a manner to be described.

The included angle between the sides of the V shaped groove 37 can bevaried, as desired, to accommodate O rings of different cross sectionaldiameters and, for example, the included angle can be in the range of 40to 80 but is preferably about 60. The bot tom of the V-shaped groove 37may be directly intersected by the passage 35, if the included angle ofgroove 37 and the cross sectional diameter of the O- ring valve 45 issuch as to permit the O-ring valve to seat in a position to block flowfrom a port defined by the intersection of the groove 37 with passage 35or, as shown, the bottom of the V-shaped groove 37 may be further cutinward, in a radial direction, to provide a supply groove 38 whichitself intersects the passage 35.

During engine operation, with the camshaft 1O ro tated to a posotion sothat the cam 9 is at zero lift posi tion relative to follower 20, asshown in HO. 1, and with the valve seated by spring 8, the lifter spring40 will effect axial separation of the follower relative to the plungerso that they engage the cam 9 and valve stem 1], respectively. Uponaxial separation of the plunger 30 relative to the follower 20 in thismanner, the volume of the fluid chamber 41 will increase resulting in areduction of the pressure of oil within the fluid chamber, it beingassumed that the fluid chamber 41 has previously been filled with oil.As this occurs, en gine oil under pressure as supplied to the branchport 17 via oil gallery 16 will enter the groove 42 to flow through port43 to groove 44 and then via passages 34 and to groove 38 and the innerportion of the V shaped groove 37 behind the O-ring valve to effectunseating of the O-ring valve 45 relative to the sides of the V-shapedgroove 37 whereby oil can flow around the O-ring valve 45 into fluidchamber 41. The O-ring valve 45 will only unseat relative to the sidesof the V- shaped groove 37 to the extent necessary to maintain the fluidchamber 41 full of oil.

During the valve opening or lift stroke of the cam 9, downwardlymovement of the follower 20 tends to force the plunger 30 further intothe follower and the resulting pressure rise ofthe oil in the fluidchamber 41 will act against the O-ring valve 45 to cause it to immediately seat against the sides of the Vshaped groove 37. With continueddownward movement of the fol lower 20, the plunger 30 is likewise moveddownwardly under the thrust of the oil trapped in the fluid chamber 41,forcing the valve 5 to unseat or open against the closing bias of spring8. As the cam continues on the valve opening or lift stroke to depressthe valve lifter 14 downward, it will effect corresponding downwardlymovement of valve 5 until such time as the lobe of the cam 9 is atmaximum lift as it engages the follower 20 of the valve lifter, thevalve 5 then being in its fully opened position.

Further rotation of the cam 9 will then bring the down-ramp thereof intoengagement with the valve lifter 14 so that the valve spring 8 is thenoperable to cause the valve 5 to start closing to effect upward movementof the valve lifter until such time as the cam 9 has rotated back into aposition with its base circle in contact with the follower 20 of thevalve lifter, thus completing the cycle.

As the above described cycle is repeated over a period of time, anyexcess of oil entering the fluid chamber 41 is forced out through aleak'down clearance provided for this purpose between the bore 25 in thefollower 20 and the outside peripheral surface of the plunger 30,whereby controlled leakage from the fluid chamber 41 into the groove 42is affected, as desired.

The plunger 30 movement within the follower 20 is limited between itsbottom position, that is, the position in which the open end of theplunger 30 is in contact with the inner surface of head 21 of thefollower 20, and its extended position, the position in which the O-ring valve 34, serving as a retainer ring .n this preferred embodimentof the valve lifter as shown in H0. 2, engages the shoulder 27 withinthe follower 20. The axial distance which the plunger 30 moves relativeto the fol lower 20 is so chosen as to insure that the installed lengthof the valve lifter will occupy the resulting space between the free endof the valve stem of the valve 5, when in its seated position, and thecam 5 in its zero lift position in all conditions of engine tolerancesand temperature.

Referring now to FIG. 3, there is illustrated a second embodiment of avalve lifter. generally designated 14', which is similar in constructionto that previously described and includes an inverted, cup-shaped,cylindrical outer member or follower 20' having a closed upper head orend wall 21', a depending outer skirt 22' and a central boss 23', theskirt 22' and central boss 23' being interconnected by spaced apart webs24' integral therewith and with the end wall 21'. The central boss 23 isprovided with a cylindrical stepped bore which includes a bore 25'extending from the free end of the boss and an enlarged bore 26' at theopposite end which terminates at the interior surface of the end wall 21the bores 25' and 26' meeting coaxially with an intervening shoulder27'. In addition, a V-shaped groove 37' is provided in the follower 20'intermediate the ends of the bore 26' and concentric therewith. The V-shaped groove 37' can be formed symmetrical or, as shown, formednon-symmetrical and, in the embodiment illustrated, the included angleof this V-shaped groove 37' is approximately 45. This nonsymmetricalconfiguration of the V-shaped groove 37' permits a more symmetricalopening where the inlet passage or port 43' from an outer annular groove42' on the outer periphery of the follower intersects or breaks into thegroove 37' thus allowing the ()-ring valve 45 positioned in this grooveto seat slightly higher within the fluid chamber 41' in the follower20', as defined in part by the open upper end of the plunger 30 slidablyreceived within the bore 25 extending into bore 26'.

In this embodiment, the plunger 30' is simply a cylindrical, cup-shapedelement having a closed lower end 31 and a stepped bore 32' extendingfrom its opposite or upper end to receive the spring 40. This plunger30' is provided on its outer periphery adjacent to its open or upper endwith an annular split ring retainer 47 positioned in a suitable annulargroove provided for this purpose whereby the split ring retainer 47forms a shoulder which extends radially outward from the plunger 30' forengagement against the shoulder 27' of follower to thereby limit axialoutward movement of the plunger 30 relative to the follower 20.

Referring now to FIG. 4, there is illustrated an alternate embodimentfrom that shown in FIG. 3 in that in this embodiment, the O-ring valve45 seats in an inverted, V-shaped groove 37 in the follower 20' in theend wall 21' thereof to open into the top end of the fluid chamber 41'.In this embodiment. the oil passage 43' intersects a second radiallyextending passage 43' a formed by a drilled bore closed at one end by aplug 48, the opposite end of this passage intersecting the V- shapedgroove 37' at the base thereof. With this construction, since the O-ringvalve 45 is positioned in the inverted, V-shaped groove 37', a valveretainer plate 5] is used to limit axial movement of the O-ring valvedownward into the fluid chamber 41'. As shown, the valve retainer plate5! is positioned on the upper end of the spring to abut against theinterior surface of the head 21' as biased by this spring to limitmovement of the O-ring valve in an unseating direction relative to theV-shaped groove. It should be realized that sufficient limited axialmovement of the O-ring valve relative to the side walls of V-shapedgroove 37' is permitted to allow unseating of the valve 45 so that oilcan flow around the O-ring valve 45 into the fluid chamber 4!v With thisarrangement of the inverted, V-shaped groove 37' in the follower 20',the oil inlet into the fluid chamber 41' is at the extreme top endthereof to thereby minimize the possibility of any trapped airaccumulating in the fluid chamber.

As in the embodiment shown in FIG. 3, the embodiment of the valve liftershown in FIG. 4 also has a split ring retainer 47 positioned in asuitable groove provided for this purpose around the outer peripheralsurface of the plunger 30 closely adjacent to its upper end.

What is claimed is:

l. A self-adjusting hydraulic valve lifter including an outer member ofcylindrical cup shape closed at one end by a head and provided with acylindrical recess at its opposite end to receive the stem of a valve,said head having a central boss integral therewith extending axiallyinto said recess, said boss having a stepped bore therein including afirst bore ofa predetermined diameter extending from the free end ofsaid boss and a second bore of a larger diameter, said first bore andsaid second bore meeting coaxially with an intervening radial extendingshoulder, a plunger of cylindrical cup shape journalled for reciprocalmovement in said first bore of said outer member in oppositelypresenting relation to said outer member, said plunger having acylindrical recess extending from one end and a head closing theopposite end thereof, said plunger being of an axial length such thatthe closed end of said inner member extends axially outward of saidfirst bore from said boss and the open end of said plunger extends intosaid second bore, said plunger defining with the peripheral surfacearound said second bore and the interior surface of said head withinsaid outer member a fluid chamber, spring means positioned in said fluidchamber for abutment against said plunger and said outer member tonormally bias said plunger in one axial direction relative to said outermember and, oil supply passage means including an O-ring valve forsupplying and maintaining a body of hydraulic fluid in said fluidchamber, said oil supply passage means including at least one supplychannel means in said outer member and at least one supply passge incommunication with a V-shaped annular groove opening into said fluidchamber, said O-ring valve being positioned in said V- shaped groove forcontrolling the one-way flow of fluid from said supply passage to saidfluid chamber.

2. A self-adjusting hydraulic valve lifter according to claim 1 whereinsaid V-shaped groove is in the outer peripheral surface of said plungeradjacent to the open end thereof and said O-ring is of an externaldiameter whereby, with said O-ring valve positioed in said V- shapedgroove, the outer periphery of said O-ring valve will extend radiallyoutward of the nominal outside di ameter of the plunger to provide ashoulder on said plunger extending into said second bore whereby tolimit axial movement of said plunger by engagement of said O-ring valvewith said shoulder, and wherein said oil supply passage means furtherincludes passage means in said plunger positioned in communication withsaid supply channel means in said outer member and with said supplypassage, and wherein said supply passage is in said plunger.

3. A self-adjusting hydraulic valve lifter in accordance with claim 1wherein said V-shaped groove is provided in the inner peripheral wallforming said second bore in said outer member, said \/-shaped groove andsaid O-ring valve positioned therein being of such a diameter so as tobe out of interference relationship with said plunger upon reciprocationof said plunger within said outer member.

4. A selfadjusting hydraulic valve lifter according to claim 1 whereinsaid V-shaped groove is in said head of said outer member at the axialend of said second bore in said boss, said V-shaped groove beingconcentric with said second bore, said supply passage extending axiallyin said head of said outer member and, wherein said valve lifter furtherincludes a valve disc retainer positioned between said spring and saidhead in position to limit axial movement of said O-ring valve.

5. A self-adjusting hydraulic valve lifter according to claim 3 furtherincluding a retainer means positioned in an annular groove in the outerperipheral surface of said plunger adjacent the open end thereof toextend radially outward of said plunger into said second bore forengagement against said shoulder whereby said plunger, said O-ring valveand said spring are retained in unit assembly with said outer member.

6. A self-adjusting hydraulic valve lifter according to claim 4 furtherincluding a retainer means positioned in an annular groove in the outerperipheral surface of said plunger adjacent the open end thereof toextend radially outward of said plunger into said second bore forengagement against said shoulder whereby said plunger, said O-ring valveand said spring are retained as a unit assembly within said outermember.

7. In an overhead valve and camshaft engine having a valve with agenerally upwardly extending valve stem, the housing of the enginehaving a lifter guide bore therein concentric with the valve stem and anengine oil supply passage extending to the lifter guide bore, a camspaced above the valve stem and, a hydraulic valve lifter interposedbetween the vale stem and the cam;

said hydraulic valve lifter comprising an inverted cupshaped outermember reciprocable in the lifter guide bore, said outer member having acentral, lower bore extending from its lower end and a larger upper boremeeting said lower bore coaxially with an intervening shoulder and ahead closing off the upper end of said outer member, said outer memberfurther having an oil supply passage means extending from said lowerbore to the outer periphery of said outer member in position to receiveoil from the engine oil supply passage, an oppositely presented.Cup-shaped. plunger having a closed head at its lower end, said plungerbeing reciprocably received in said lower bore with its upper end extending into said upper bore to define therewith a fluid chamber, saidplunger having a V-shaped groove in the outer periphery thereof openinginto said fluid chamber and a passage means therein opening at one endinto the apex of said V-shaped groove and terminating at its other endin a side port in communication with said oil supply passage means insaid outer member. an O-ring valve positioned in said V-shaped groove,said O-ring valve serving as a one-way check valve to control oil flowfrom said V-shaped groove into said fluid chamber and also serving as ashoulder extending radially outward from said plunger to limit axialmovement of said plunger in one direction by engagement of said O-ringvalve with said shoulder in said outer member and, a spring positionedin said fluid chamber to abut against said outer member and said plungerfor normally maintaining said head of said outer member abutting the camand said closed head of said plunger abutting the valve stem.

1. A self-adjusting hydraulic valve lifter including an outer member ofcylindrical cup shape closed at one end by a head and provided with acylindrical recess at its opposite end to receive the stem of a valve,said head having a central boss integral therewith extending axiallyinto said recess, said boss having a stepped bore therein including afirst bore of a predetermined diameter extending from the free end ofsaid boss and a second bore of a larger diameter, said first bore andsaid second bore meeting coaxially with an intervening radial extendingshoulder, a plunger of cylindrical cup shape journalled for reciprocalmovement in said first bore of said outer member in oppositelypresenting relation to said outer member, said plunger having acylindrical recess extending from one end and a head closing theopposite end thereof, said plunger being of an axial length such thatthe closed end of said inner member extends axially outward of saidfirst bore from said boss and the open end of said plunger extends intosaid second bore, said plunger defining with the peripheral surfacearound said second bore and the interior surface of said head withinsaid outer member a fluid chamber, spring means positioned in said fluidchamber for abutment against said plunger and said outer member tonormally bias said plunger in one axial direction relative to said outermember and, oil supply passage means including an O-ring valve forsupplying and maintaining a body of hydraulic fluid in said fluidchamber, said oil supply passage means including at least one supplychannel means in said outer member and at least one supply passge incommunication with a V-shaped annular groove opening into said fluidchamber, said O-ring valve being positioned in said Vshaped groove forcontrolling the one-way flow of fluid from said supply passage to saidfluid chamber.
 2. A self-adjusting hydraulic valve lifter according toclaim 1 wherein said V-shaped groove is in the outer peripheral surfaceof said plunger adjacent to the open end thereof and said O-ring is ofan external diameter whereby, with said O-ring valve positioed in saidV-shaped groove, the outer periphery of said O-ring valve will extendradially outward of the nominal outside diameter of the plunger toprovide a shoulder on said plunger extending into said second borewhereby to limit axial movement of said plunger by engagement of saidO-ring valve with said shoulder, and wherein said oil supply passagemeans further includes passage means in said plunger positioned incommunication with said supply channel means in said outer member andwith said supply passage, and wherein said supply passage is in saidplunger.
 3. A self-adjusting hydraulic valve lifter in accordance withclaim 1 wherein said V-shaped groove is provided in the inner peripheralwall forming said second bore in said outer member, said V-shaped grooveand said O-ring valve positioned therein being of such a diameter so asto be out of interference relationship with said plunger uponreciprocation of said plunger within said outer member.
 4. Aself-adjusting hydraulic valve lifter according to claim 1 wherein saidV-shaped groove is in said head of said outer member at the axial end ofsaid second bore in said boss, said V-shaped groove being concentricwith said second bore, said supply passage extending axially in saidhead of said outer member and, wherein said valve lifter furtherincludes a valve disc retainer positioned between said spring and saidhead in position to limit axial movement of said O-ring valve.
 5. Aself-adjusting hydraulic valve lifter according to claim 3 furtherincluding a retainer means positioned in an annular groove in the outerperipheral surface of said plunger adjacent the open end thereof toextend radially outward of said plunger into said second bore forengagement against said shoulder whereby said plunger, said O-ring valveand said spring are retained in unit assembly with said outer member. 6.A self-adjusting hydraulic valve lifter according to claim 4 furtherincluding a retainer means positioned in an annular groove in the outerperipheral surface of said plunger adjacent the open end thereof toextend radially outward of said plunger into said second bore forengagement against said shoulder whereby said plunger, said O-ring valveand said spring are retained as a unit assembly within said outermember.
 7. In an overhead valve and camshaft engine having a valve witha generally upwardly extending valve stem, the housing of the enginehaving a lifter guide bore therein concentric with the valve stem and anengine oil supply passage extending to the lifter guide bore, a camspaced above the valve stem and, a hydraulic valve lifter interposedbetween the vale stem and the cam; said hydraulic valve liftercomprising an inverted cup-shaped outer member reciprocable in thelifter guide bore, said outer member having a central, lower boreextending from its lower end and a larger upper bore meeting said lowerbore coaxially with an intervening shoulder and a head closing off theupper end of said outer member, said outer member further having an oilsupply passage means extending from said lower bore to the outerperiphery of said outer member in position to receive oil from theengine oil supply passage, an oppositely presented, cup-shaped, plungerhaving a closed head at its lower end, said plunger being reciprocablyreceived in said lower bore with its upper end extending into said upperbore to define therewith a fluid chamber, said plunger having a V-shapedgroove in the outer periphery thereof opening into said fluid chamberand a passage means therein opening at one end into the apex of saidV-shaped groove and terminating at its other end in a side port incommunication with said oil supply passage means in said outer member,an O-ring valve positioned in said V-shaped groove, said O-ring valveserving as a one-way check valve to control oil flow from said V-shapedgroove into said fluid chamber and also serving as a shoulder extendingradially outward from said plunger to limit axial movement of saidplunger in one direction by engagement of said O-ring valve with saidshoulder in said outer member and, a spring positioned in said fluidchamber to abut against said outer member and said plunger for normallymaintaining said head of said outer member abutting the cam and saidclosed head of said plunger abutting the valve stem.